Longitudinal in-situ impedance and resin monitoring sensor, and method of measuring and tracking the movement of hardness in a water softener utilizing the same

ABSTRACT

A sensor system and process that utilizes impedance/conductivity measurements to track the movement of hardness in an ion exchange media. The impedance/conductivity sensor is a vertical, longitudinally directed, axially lengthwise electrode system having electrodes placed within a bed of ion exchange material and separated by water and the ion exchange material. The electrodes generally run parallel to one another. Hard water is introduced to the water softener and softened by the ion exchange material. A hardness gradient is tracked by the sensor, and regeneration is initiated when it is determined that the ion exchange material is depleted or exhausted.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a sensor system and process thatutilize an impedance sensor to track the movement of hardness in an ionexchange media, such as a water softener, water refiner, or similar typesystem, including systems encompassing conductive material and aredesigned to be regenerable. The impedance measurements may be coupledwith, and/or used to determine, measurements of capacity of the ionexchange media and measured water flow, ultimately to ascertain thelevel of hardness of the incoming water.

2. Description of Related Art

Water systems using groundwater as a source are generally susceptible ofwater hardness. As water moves through soil and rock it dissolves smallamounts of naturally-occurring minerals and carries them into thegroundwater supply. Water is known to be a great solvent for calcium andmagnesium, so if the minerals are present in the soil around awater-supply well, the hard water may be delivered to homes. Therefore,water hardness varies as a function of geography. For example, in areaswithin the United States where the water is relatively hard, industriesmight have to spend money to soften their water, as hard water candamage equipment. Hard water is known to shorten the life of waterheaters, fabrics and clothes and clog other water equipment, such asshower and sink faucets.

Furthermore, incoming hardness may fluctuate due to changes in blendingof different water sources. For example, in the winter a ground watersource may be used and in the summer a surface water source may be used.The hardness of these water sources is most likely different at least inconcentration, if not in type of minerals as well. Additionally, amunicipality generally has more than one water source, feeding from anumber of wells. These wells typically have different hardnessconcentrations. Depending on which well is supplying water, the hardnessin the source water delivered to a water softener will fluctuate. Thismakes for appreciable variations in feed water hardness.

Calcium and magnesium dissolved in water are the two most commonminerals that make water “hard.” The degree of hardness becomes greateras the calcium and magnesium content increases and is related to theconcentration of multivalent cations dissolved in the water.

The hardness of water is generally referred to by three types ofmeasurements: grains per gallon, milligrams per liter (mg/L), or partsper million (ppm). General guidelines for classification of waters aretypically: 0 to 60 mg/L (milligrams per liter) of calcium carbonate isclassified as soft; 61 to 120 mg/L is classified as moderately hard; 121to 180 mg/L is classified as hard; and more than 180 mg/L is classifiedas very hard.

Table I below depicts the general hardness classification categories ofwater:

TABLE 1 Milligrams per Liter (mg/L) or Parts per Million Grains perGallon (ppm) Classification   0-3.5  0-60 Soft to Slightly Hard 3.5-7.0 60-120 Moderately Hard  7.0-10.5 120-180 Hard over 10.5 over 180 VeryHard

Hard water may form deposits that clog plumbing. These deposits,referred to as “scale”, are composed mainly of calcium carbonate(CaCO₃), magnesium hydroxide (Mg(OH)₂), and calcium sulfate (CaSO₄).Calcium and magnesium carbonates tend to be deposited as off-whitesolids on the inside surfaces of pipes and heat exchangers. Thisprecipitation (formation of an insoluble solid) is principally caused bythermal decomposition of bicarbonate ions but also happens in caseswhere the carbonate ion is at saturation concentration. The resultingbuild-up of scale restricts the flow of water in pipes. In boilers, thedeposits impair the flow of heat into water, reducing the heatingefficiency and allowing the metal boiler components to overheat. In apressurized system, this overheating can lead to failure of the boiler.

The presence of ions in an electrolyte, in this case, hard water, canalso lead to galvanic corrosion, in which one metal will preferentiallycorrode when in contact with another type of metal, when both are incontact with an electrolyte.

Conductivity is a measure of water's capability to pass electrical flow.This ability is directly related to the concentration of ions in thewater. These conductive ions come from dissolved salts and inorganicmaterials such as alkalis, chlorides, sulfides, and carbonate compounds.The more ions that are present, the higher the conductivity of water.Likewise, the fewer ions that are in the water, the less conductive itis. Distilled or deionized water can act as an insulator due to its verylow (if not negligible) conductivity value. In contrast, sea water has avery high conductivity.

Conductivity can also measure total dissolved solids (TDS). Totaldissolved solids combine the sum of all ionized particles that aregenerally smaller than 2 microns. This includes all of the disassociatedelectrolytes that make up salinity concentrations, as well as othercompounds such as dissolved organic matter. The higher the level of TDS(ppm), the higher the degree of water hardness. (Using the chart above,1 grain of hardness is approximately 17.1 ppm (mg/L) in TDS.) This meansthat the measure of conductivity directly correlates to the measure ofions that contribute to water hardness.

In North America and many other countries, the water quality changesseasonally as sources are changed or weather conditions change. Thus,while a softener supplier or customer sets up or performs the initialsoftener commissioning step in order for the softener to optimallyperform at the hardness measured during the installation, any subsequentchanges in the feed water will result in poor performance—either thecustomer will periodically get untreated water or they will have poorwater and salt efficiencies.

Many consumers use water softeners to soften the water used in theirhomes, the work place, schools, etc. These water softeners are typicallypreset to soften water of a predefined degree of hardness.

A water softener includes a resin tank or vessel that is filled with ionexchange resin comprising thousands of small spherical polymeric beadsof cross-lined polystyrene sulfonic acid, and is generally referred toas a cation resin. The cation resin is added to a processing vessel,such as within a water softener. The vessel generally has internalpiping and fine screens to prevent the resin beads from washing away.

The resin is usually placed into service with Na⁺ ions on the beads.When hardness ions come into contact with the Na⁺ ions bound to theresin, they exchange—that is, one calcium ion displaces two Na⁺ ionsthat were originally bound to the resin bead, and the Na⁺ ions aresubsequently released into the water. In some instances, potassium (K)is used as the exchange ion.

Incoming water flows down through the resin bed and leaves eitherthrough the bottom outlet of the vessel or through a transfer tube backup to the top of the vessel. This is generally referred to as a servicecycle. As the incoming water rich in calcium and magnesium passesthrough the bed, it contacts the resin bead surfaces and the mineralsare replaced by the sodium ions.

In addition to hardness ions, the resin exchange process also picks upiron ions if they are present in the water and reduces the capacity ofthe resin bed for hardness exchange.

Importantly, the chemical reaction within this vessel is reversible.Like any chemical process, the resin has a finite capacity to exchangecalcium (Ca⁺⁺) and magnesium (Mg⁺⁺) for the equivalent of sodium (Na⁺).Eventually the resin becomes saturated with Ca⁺⁺ and Mg⁺⁺ and will nolonger be removed. At that point the resin is exhausted and requiresregeneration.

In this process there is a point of hardness breakthrough or saturation.When hardness breakthrough occurs, the resin is saturated andnon-removed Ca⁺⁺ and Mg⁺⁺ pass directly through the bed and raise thehardness level of the effluent water leaving the softener.

When the hardness minerals are trapped in the resin and removed from thewater, the water becomes “soft”. However, once the water softener resingets completely exchanged or covered with hardness minerals it needs tobe regenerated.

During the regeneration process, the water softener floods the resinwith brine water, a saturated concentration of either Na⁺ or K that isslowly passed through the system. This saturated solution performs areverse ion exchange, replacing the calcium and magnesium with Na⁺ or K,and the hardness flows out of the system to drain. After a thoroughrinse to remove any excess brine, the softening resin in the watersoftener is then ready to soften water again.

When a water softener is first installed, the hardness of the incomingwater is typically tested and input as one component of the softener'soperating algorithm or regeneration timer. This hardness measurement,for example, the measurement of iron, if tested, consumes a small volumeof a softener's resin capacity and provides a reasonable estimation ofthe system's capacity at startup. While in other softener installations,the hardness is only estimated, which will typically result in lessefficient operation and performance.

However, some incoming water chemistry can change dramatically fromseason to season, or even during a single day, based on a municipalitychanging or blending their raw water sources. In addition, somecustomers and/or government entities wish to have water that is onlypartially softened, typically to minimize the amount of sodium in thesoftened water, and do so by blending untreated water with softenedwater, typically using a manual blending valve that is set statically atthe time of installation based on the hardness values at that time.Knowing the true hardness of the water in real-time, perhaps ifpossible, based on the rate of resin bed depletion, would improve theaccuracy of the blending and even allow for blending in-situ using anautomated blending valve controlled by the system's electronics andalgorithms.

Finally, it is known that resin ages over time and is not able to fullyregenerate, thereby losing some of its capacity. It is desirable tounderstand this capacity change based on the volume of sodium used toregenerate versus the measured capacity of the softener actuallyregenerated, such that a softener's learning algorithm can be determinedto modify the regeneration cycle and maintain and/or optimize thesoftener's capacity over time. Accordingly, a one-time measurement ofwater hardness is not sufficient for optimal system performance, nor isit amenable for in-situ blending.

Point sensors that detect changes in conductivity in an ion exchangeresin bed are typically situated in the bed so that about 20% of thevolumetric capacity of the bed is held in reserve.

The height at which the point sensor is placed may be set at a higherheight if the water hardness is significantly higher than 20 gpg. If thewater is at a lower hardness level it may be set at a slightly lowerheight. When the point sensor detects that the softener has beenexhausted at that bed height then the system may be set to regenerateimmediately or at a delayed regeneration time.

As noted, these sensors are point-locators that register when depletionof the resin bed reaches a predetermined level.

Regeneration can be initiated based on time of day, time intervals, ortotal flow through the exchange tank. In some applications, especiallywhen there is a variable concentration of ions to be removed, time orflow-based intervals may not be satisfactory. Under these conditions,either regeneration may not occur until after the tank has beenexhausted or energy and resources may be wasted by regenerating too soonor too often.

SUMMARY OF THE INVENTION

Bearing in mind the problems and deficiencies of the prior art, it istherefore an object of the present invention to provide a sensor systemand process that utilizes conductivity, impedance, or both, to track themovement of hardness in an ion exchange material within a watersoftener.

Another object of the present invention is to provide a method formeasuring and tracking the movement of hardness in ion exchangematerial, typically known as the “Hardness Front” in a water softenerusing conductivity and/or impedance measurements.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the specification.

The above and other objects, which will be apparent to those skilled inthe art, are achieved in the present invention which is directed to anapparatus for producing a signal indicative of a state of the exhaustionor depletion of an ion exchange material in a vessel, comprising: thevessel having an axial length traversing in a longitudinal directionfrom approximately vessel top to approximately vessel bottom; the ionexchange material within the vessel; a conductivity, resistivity, and/orimpedance sensor for determining the exhaustion or depletion of the ionexchange material, the conductivity or impedance sensor including atleast two electrodes in electrical communication with one another,wherein the electrodes extend continuously approximately throughout theaxial length of the vessel in the longitudinal direction; and acontroller for producing a signal to the electrodes and/or receiving asignal from the electrodes representing a conductivity or impedancemeasurement between the electrodes.

The apparatus includes a hard water input; a soft water output; aregeneration supply solution for regenerating the ion exchange resin; adrain or regenerating waste stream; a water softener or regenerationvalve; and an admixing or blending device for mixing output fluid.

Each of the electrodes may comprise a wire conductor formed ofconductive material which are situated to run generally parallel to oneanother.

In at least one embodiment, the electrodes traverse along or inside atube internal to the vessel while in contact with the ion exchangematerial, and are set apart as the electrodes progress approximatelythroughout the axial length of the vessel in the longitudinal direction.

The electrodes may progress approximately throughout the axial length ofthe vessel in the longitudinal direction approximately parallel to oneanother.

The electrodes may progress approximately throughout the axial length ofthe vessel in the longitudinal direction, wherein each electrode isformed of sequential curved and straight segments such that the curvedsegments of each electrode are parallel to one another and the straightsegments of each electrode are parallel to one another.

Alternatively, the electrodes progress approximately throughout theaxial length of the vessel in the longitudinal direction, wherein theelectrodes are separated a predetermined distance that varies throughoutthe axial length of the vessel in the longitudinal direction.

The apparatus may include a plurality of electrode pairs havingdifferent lengths extending in the longitudinal direction such that atleast one electrode pair progresses approximately throughout the axiallength of the vessel in the longitudinal direction, and other electrodepairs have varying lengths shorter than a longest length electrode pair.

The controller includes operational software to calculate the averageimpedance, conductivity, or resistivity of the ion exchange materialwithin the vessel, wherein the average impedance, conductivity, orresistivity is proportional an amount of regeneration of the ionexchange material within the vessel.

The controller may include operational software to track resistivity ofthe ion exchange material as a function of water volume through theapparatus.

The controller may include operational software to calculate and monitorthe relationship between resistivity of the ion exchange material andcapacity of the ion exchange material being depleted.

The controller may further include operational software to compare inputvolume of water flowing into the vessel to capacity of ion exchangematerial being used or depleted, and from this comparison, compare thecapacity to resistivity measured by the conductivity, resistivity, andor impedance sensor, such that capacity of the ion exchange material canbe ascertained in-situ.

In a second aspect, the present invention is directed to an apparatusfor producing a signal indicative of the state of the exhaustion ordepletion of an ion exchange material in a vessel, comprising: thevessel having an axial length traversing in a longitudinal directionfrom approximately vessel top to approximately vessel bottom; the ionexchange material within the vessel; a conductivity or impedance sensorfor determining the exhaustion or depletion of the ion exchangematerial, the conductivity or impedance sensor including at least twoelectrodes in electrical communication with one another, wherein theelectrical communication between the electrodes is interrupted by aplurality of insulators space apart axially to form non-conductive gapsbetween the electrodes that extinguish conduction between adjacentinsulation portions on each electrode to enable segment-wise continuouselectrical communication between electrode portions not interrupted byinsulators throughout the axial length of the vessel in the longitudinaldirection; and a controller for producing a signal to the electrodesand/or receiving a signal from the electrodes representing aconductivity or impedance measurement between the electrodes.

This apparatus may include: a hard water input; a soft water output; aregeneration supply solution for regenerating the ion exchange resin; adrain or regenerating waste stream; a water softener or regenerationvalve; an admixing or blending device for mixing output fluid; and alower diffuser plate.

In a third aspect, the present invention is directed to a watertreatment system having a tank containing a particle bed for removingminerals from water flowing through the tank, and a measuring apparatusfor measuring conductivity and/or impedance within the tank, comprising:a hard water input; a soft water output; the particle bed including ionexchange material within the tank; a regeneration supply solution forregenerating the ion exchange material; a drain or regenerating wastestream; a water softener or regeneration valve; an admixing or blendingdevice for mixing output fluid; the tank having an axial lengthtraversing in a longitudinal direction from approximately tank top toapproximately tank bottom; a conductivity or impedance sensor fordetermining exhaustion or depletion of the ion exchange material, theconductivity or impedance sensor including at least two electrodes inelectrical communication with one another, wherein the electrodes extendcontinuously approximately throughout the axial length of the vessel inthe longitudinal direction, the electrodes in contact directly with theion exchange material for impedance measurements or indirectly with theion exchange material for conductivity measurements; and a controllerfor producing a signal to the electrodes and/or receiving a signal fromthe electrodes representing a conductivity or impedance measurementbetween the electrodes.

The water treatment system may include a tube traversing in thelongitudinal direction from approximately the tank top to approximatelythe tank bottom, the tube directing fluid flow either upwards towardsthe tank top, or downwards toward the tank bottom. And, the electrodescan be supported by the tube.

Conductivity measured by the electrodes corresponds to a change in ionexchange material from Na⁺ to Ca²⁺ and/or Mg²⁺.

In a fourth aspect, the present invention is directed to a method formeasuring and tracking the movement of hardness in a water softener, themethod comprising: introducing hard water from a point of entry into avessel containing a particle bed of ion exchange material; electricallyconnecting a controller to electrodes; situating the electrodes withinthe vessel such that the electrodes traverse an axial length of thevessel in a longitudinal direction from approximately vessel top toapproximately vessel bottom within the particle bed of ion exchangematerial; measuring impedance, conductivity, and/or resistivity betweenelectrodes using the controller; calculating from the impedance,conductivity, and/or resistivity measurements a state of the exhaustionor depletion of the ion exchange material in the vessel; initiating aregeneration of the ion exchange material upon determination ofexhaustion or depletion of the ion exchange material.

The step of initiating the regeneration further includes ceasing inflowof the water and pumping a regenerate into the ion exchange material.

The method further includes: utilizing historical data on water usage asa function of time to assist in determining the step of initiation ofthe regeneration; pumping the regenerate into the ion exchange materialfrom a direction opposite that of water flow during normal operation;and/or monitoring the impedance, conductivity, and/or resistivity todetermine when a regenerate trailing edge or front is removed from theion exchange material.

The method may include initiating a slow rinse followed by a fast rinse,and monitoring the conductivity and/or impedance during either or bothof the rinses to determine when either or both of the rinses arecomplete based on impedance, conductivity, and/or resistivity changes.

The method may also include introducing hard water to the watersoftener, and identifying a new hardness front by measuring impedance,conductivity, and/or resistivity between the electrodes.

The method may include introducing a blending valve to blend the hardwater with softened water if a mixture of hard water/softened watercombination is desired.

The method may include calculating and monitoring the relationshipbetween impedance, conductivity, and/or resistivity of the ion exchangematerial and capacity of the ion exchange material being depleted.

The method may also include comparing input volume of water flowing intothe vessel to capacity of ion exchange material being used or depleted,and from this comparison, comparing the capacity to impedance,conductivity, and/or resistivity measured by the electrodes, such thatcapacity of the ion exchange material can be ascertained in-situ; and/orcalculating the run-to-run conductivity of a given amount of brinesolution to resin capacity to gauge the use life of the resin andsuggest replacement time.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the invention believed to be novel and the elementscharacteristic of the invention are set forth with particularity in theappended claims. The figures are for illustration purposes only and arenot drawn to scale. The invention itself, however, both as toorganization and method of operation, may best be understood byreference to the detailed description which follows taken in conjunctionwith the accompanying drawings in which:

FIG. 1 depicts a cross-sectional, perspective view of one embodiment ofa longitudinal impedance sensor for use in a water softener tank;

FIG. 2A depicts a segmented design for the electrodes used in alongitudinal impedance sensor, where each electrode is patterned toinclude substantially straight portions and complementary opposingconcave curvatures that are curved to form an electrode separation gapgreater than that provided by the substantially straight portions;

FIG. 2B depicts an electrode geometry used in a longitudinal impedancesensor where the electrodes diverge from one another over the course ofthe length of the electrodes as they traverse the length of the vessel;

FIG. 2C depicts an electrode geometry used in a longitudinal impedancesensor where a plurality of electrodes is presented having differentlengths traversing the length of the vessel as another way to ascertainthe location of the regeneration gradient;

FIG. 3 depicts a printed electrode geometry for use in a longitudinalimpedance sensor produced by silk screening a silver containing ink, orother conductive materials, onto a mylar or other non-conductive sheet,and then overprinted with a carbon containing ink, such that theelectrodes are exposed externally on the mylar sheet;

FIG. 4 depicts an illustrative example of a segmented insulated parallelelectrode configuration (one or more insulated sections) used to measureand estimate the breakthrough volume of a resin bed;

FIG. 5 is a graph of the predicted breakthrough, comparing impedance andthe output flow of Ca²⁺ in units of ppm, both measured as a function oftime;

FIG. 6 depicts a simplified electronic circuit used to stimulate anelectrode response (Vo) at approximately 100 mV between electrodeconductors within exhausted resin;

FIG. 7 depicts the response of the electrodes (V_(o)) plotted againstwater volume (L) passing through the resin bed with water quality ofabout 25 g at room temperature (25° C.) and with a TDS of about 1000ppm;

FIG. 8 depicts a chart identifying the estimated total hardness, actualtotal hardness, corrected total hardness, and percent deviation for eachrun performed at different temperatures for the example test runsdepicted in FIG. 7 ;

FIG. 9 depicts the response of the electrode V_(o) (mV) versus the resincapacity (unused) R_(c) (g) for the example test runs depicted in FIG. 7until breakthrough by trimming the initial volume of water;

FIG. 10 depicts a table (Table 1) comparing V_(o) values to estimateresin capacity (R_(c)) and total hardness (TH), wherein Run 27identified in FIG. 4 along with an additional Run 64 are compared byrecording two to three V_(o) values to estimate resin capacity (R_(c))and total hardness (TH);

FIG. 11 depicts temperature compensated calculations for Runs 27 and 64from 40.8° C. to 25° C. utilizing equations (1) and (3);

FIG. 12 depicts a table for the correction factor for temperaturecompensation presenting the accuracy of the method by limitingdeviations to less than or equal to 10%;

FIG. 13 presents a comparison of TH deviation (%) with and without thecorrection factor over several tests conducted at various temperatures(approximately 10° C., 25° C., and 40° C.) with different TH (about 10g, 15 g, and 25 g);

FIG. 14 depicts the results of output potential V_(o) (mV) as a functionof volume (L), and indicating breakthrough for three different runs;

FIG. 15 depicts the results of resin capacity R_(c) as a function of Vo(mV);

FIG. 16 depicts the effects of TDS on R_(c) versus V_(o), aftertemperature compensation;

FIG. 17 depicts results from the tests conducted under FIG. 16 with 1500ppm and 2000 ppm of TDS;

FIG. 18 depicts an electrode configuration for establishing an earlybreakthrough point where the electrode is terminated a distance from thelower diffuser.

FIG. 19 depicts the stabilizing of V_(o) (by approximately 8% by volume)before breakthrough (soft water with TH of ˜1 g);

FIG. 20 depicts the effect of flow rate of the electrode responseservice cycle on V_(o) v. V_(L);

FIG. 21 depicts the effect of flow rate and FIG. 21 depicts the effectof flow rate on R_(c) v. V_(L);

FIG. 22 depicts the effect of flow conditions on V_(o) v. V_(L);

FIG. 23 depicts the effect of flow conditions on R_(c) v. V_(o);

FIG. 24 depicts a plot to find early breakthrough measuring cold watertemperature versus time;

FIG. 25 depicts a plot to show the operational window for the electrodeof the present invention, plotting optimal time for uniform temperatureas a function of volume of water passed through the resin bed;

FIG. 26 depicts a number of runs for the total hardness of blended waterfor 2 g and 5 g respectively at 10° C., 25° C., and 40° C.;

FIG. 27 depicts a number of runs for the total hardness of blended waterwith high TDS for 2 g and 5 g respectively at 10° C. and 40° C.; and

FIG. 28 is a flow chart depicting the flow procedure for estimating thetotal hardness upstream of the softener.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

In describing the preferred embodiment of the present invention,reference will be made herein to FIGS. 1-28 of the drawings in whichlike numerals refer to like features of the invention.

A hardness sensor directed longitudinally or lengthwise through a resinbed-based water softener vessel, and a process to optimize the hardnessmeasurement is presented. Water softeners, water refiners, or similartype systems, including systems that are regenerable, are considered.Together, the sensor, process, and monitored flow rate of such a systemcan be used to predict when a water softener will exhaust its capacityand require regeneration or replacement. The prediction of exhaustioncan also be used to cause a regeneration of the system prior toexhaustion, and/or at a convenient time when water is not required, sothat treated water is always supplied. In addition, the sensor andprocess can be used to monitor how much of the system's capacity hasactually been regenerated during a regeneration cycle rather thanassuming averages based on the estimated volumes or weight of aregenerant being injected into the system during a regenerating cycle.The sensor, process, and monitored flow rate can also be used tocommission a water softener, without having to input an initial hardnessmeasurement, by automatically calculating incoming water hardness basedon the rate of exhaustion of the bed and the flow of water through thesystem. In addition, the device and process can be used to monitor andadjust for water hardness, including hardness changes during a day,aging of the resin bed, and other factors affecting the holding capacityof the resin, including water velocity, that can impact performance andcapacity. Such capability can also be used to accurately blend treatedand untreated water in-situ in order to achieve a desired outputhardness from the system where fully softened water is not desired.Furthermore, by knowing the incoming hardness and how it changes overtime, one can estimate the outgoing sodium level contributed by thesoftener and allow users to blend softened and unsoftened water, eithermanually or with an automated blending valve, to achieve a lower sodiumlevel in their water if desirable. Moreover, the location of thehardness threshold in the resin bed may be ascertained, which mayfacilitate predictive capabilities of the water softener system.

The sensor of the present invention will now be described in conjunctionwith a water-softening apparatus. It is to be understood that the watersoftening apparatus described in conjunction with the description of thesensor of the present invention is but one example of a resin-type ionexchange apparatus to which the sensor of the present invention may beapplied, and the invention is not limited solely to water softeners.

Softener regeneration, the process of removing calcium, magnesium, iron(and possibly other ions) from absorbing resin is an area of watertreatment where improved monitoring is beneficial. The processescurrently in the art are often imprecise since they are based on anapproximation of how much sodium or other chemical was used inregeneration. Furthermore, it is inefficient to attempt to regeneratethe entire resin bed since this requires a disproportionate amount ofsodium to do so and most modern softeners tend to only partly regeneratein order to have an efficient use of sodium.

A resin bed cannot typically be one hundred percent (100%) regeneratedin normal use, even with what is known as a “maximum salt dose.” Thus,knowing how much of the resin bed was actually regenerated by monitoringthe movement of sodium through the bed with a longitudinally directedsensor design having electrodes that may or may not be segmented, and/orby looking at the time it took for the sodium to reach the top of thesensor, and how long it took for the bottom of the sensor to react to aclearing of the “salt front”, would improve the system's accuracy andtroubleshooting capability. It would also provide the system's algorithmwith valuable information about the true capacity of the regeneratedresin bed for more efficient operation.

The ability to accurately monitor the remaining capacity of a softener,along with a learning algorithm that can predict the timing of waterusage-based customer usage patterns, would allow regeneration atdifferent times during a day rather than setting the regeneration for afixed time.

In this manner, the present invention encompasses a water softenerdevice having an ion exchange resin bed, a regeneration solution supplyfor regenerating the ion exchange resin when it is depleted, an admixingor blending device for mixing output water, and an impedance sensor(capable of measuring conductivity, resistivity, capacitance) fordetermining the depletion of the ion exchange resin bed throughconductive measurements. The impedance sensor is preferably in the formof a vertical, longitudinally directed (e.g., axially lengthwise withrespect to the water softener vessel), electrode system, referred hereinas a longitudinal impedance sensor. It should be noted thatconductivity, resistivity, and/or capacitance measurements—allrelational to impedance—may be empirically determined, and suchmeasurement that ultimately infer impedance are within the scope of thepresent invention.

FIG. 1 depicts a cross-sectional, perspective view of one embodiment ofa longitudinal impedance sensor for use in a water softener tank 10having a resin bed 12 a,b,c of ion exchange material for removinghardness, where as an exemplary embodiment, a portion of resin bed 12a,b,c is shown having distinct sections. The ion exchange material iscapable of receiving hard water ions during the softening operation andreleasing the hard water ions during the regeneration operation of thewater softener. Generally, the ion exchange material comprises polymerbeads with functional groups attached to provide the ion exchangefunction. The ion exchange may be cation- or anion-exchange dependingupon the particular functional group selected. Ion exchange resin isutilized in the preferred embodiment, although the operation of alongitudinal impedance sensor is not prohibited by using other ionexchange material.

Hard water 7 is introduced to the water softener device through valve 4,which can be a water softener valve, operation valve, and/orregeneration valve, or a combination thereof. Brine or regenerationsolution 5 enters valve 4 as needed into the water softener device tank10. A regenerating waste stream 6 exits valve 4, as well as the treatedsoft water output 9. The direction of regeneration may be concurrentwith the initial water flow (co-flow) or counter to the initial waterflow (counter-flow).

Section 12 a of the resin bed is that portion of the resin bed that ispopulated with sodium ions (salts). Sodium salts are preferred, and areubiquitous in water softeners; however, other soluble salts may beutilized, such as for example a potassium salt. Water, when added withinthe water softener tank, combines with the salt to form a saturatedbrine. During regeneration, the brine brought in contact with the ionexchange resin. Section 12 b is that portion of resin bed that has hadits sodium ions exchanged (depleted), and thus holds the exchangedhardness ions.

A hardness gradient front or region, exemplifying the exchange, isdepicted by section 12 c. In a first embodiment, a segmentedlongitudinal impedance sensor 14 is introduce situated on the outside ofa central support tube 18 in direct contact with the resin and traversesaxially (longitudinally) approximately from the top to the bottom oftank 10. This may be along the tank's central axis in a definedlongitudinal direction on central tube 18, or may be at a location offthe center axis.

Longitudinal impedance sensor 14 is preferably constructed of at leasttwo wire conductors 16 formed from conductive material and generallyrunning parallel to one another. In the embodiment depicted in FIG. 1 ,the conductors 16 traverse along tube 18, and are set apart apredetermined distance as they progress vertically down through theresin bed. As depicted in FIG. 1 , in this first embodiment longitudinalimpedance sensor wires or conductors 16 are segmented with insulators 22spaced apart vertically providing for non-conductive gaps in theconductive sensor. The insulators 22 serve to extinguish any conductionbetween adjacent insulation portions on each wire 16. In this manner,the electrical communication between electrodes is segment-wisecontinuous. The segmented longitudinal impedance wires or conductorsprovide for a digitization of the conductor output and assist inlocating more precisely the hardness gradient insomuch as there exists aconductive “gap” at each insulator section helping to establish adigital reading; however, a non-segmented design, where the impedancesensor wires or conductors axially traverse the vessel uninterrupted,can be employed with sufficiently effective results.

External input/output (I/O) sensor wires 20 are connected electricallyto the longitudinal impedance sensor wires 16. Sensor wires 20 extendoutside tank 10 and connect with electronics (not shown) that drivesignals through the longitudinal impedance wires 16. The external sensorwires 20, connected to signal electronics, establish a signal in thelongitudinal impedance wires 16 to create a measurable impedance,resistivity, and/or conductance between the wires, whether between apair of wires or multiple wires.

The conductors are situated within an ion exchange resin tank 10 and arein contact directly with the resin. The conductors may be imbedded forconductance, partially blocked with insulators 22 as depicted in FIG. 1, or in a second embodiment, fully exposed without an insulator segment.

In a separate embodiment, tube 18 may actually represent two separatefluid flow paths—one flow path for upward flow, and a second flow pathfor downward flow, depending upon the softener design. In the embodimentof FIG. 1 , resin bed portion 12 a depicts depleted or exchanged resinof a downward flow design, insomuch as the depleted portion is above thehardness gradient 12 c and the non-depleted resin 12 b. A reversescenario would occur for an upward flow configuration.

A bottom plate 24 is shown employed to redirect water flow from theoutside of tube 18 into tube 18 and upward towards a water softenervalve in the direction of arrow 26.

In an exemplary embodiment of a vertical, longitudinal conductor design,a set of two vertical conductors or electrodes were fixed in a resin bedto a central riser tube, wherein the conductivity measured by the twovertical electrodes responds to a change in resin form from Na⁺ to Ca²⁺or Mg²⁺. Each conductor being comprised of a stainless steel flat orshaped profile strand (e.g., SS-304), having an exemplary length on theorder of 24 cm±2 mm, and in the case of a shaped wire profile, having adiameter of about 2.0 mm±0.1 mm.

It has been further realized that although stainless steel materialyielded favorable results, the material is not adequately corrosionresistant in a water softener environment. The iron lead to considerablerapid corrosion to the electrodes. In this regard, electrodes platedwith a more inert metal coating, such as a noble metal, will detercorrosion. Electrodes, including those having a titanium or copper basemetal, may be plated with platinum, gold, or other inert or lesscorrosive material.

Distance between electrodes in the exemplary embodiment was 12.5 mm±0.2mm; however, depending upon the characteristics of the electrodematerial, the signal strength, and sensor electronics sensitivity, thedesign may allow for the distance between the conductors to be closertogether or further apart. These electrodes were fixed to the raiser orcentral tube 18 above the lower diffuser plate as shown in FIG. 1 .Electrodes were made sure not to be exposed to water outside the resinbed and to remain in the resin bed. This was accomplished by limitingthe active electrode length—the length of the electrode capable ofsignal transmission—to approximately 2 cm below resin bed top surface.Additionally, the bottom of the electrode is located approximately 2.5cm above lower diffuser plate.

FIG. 2 depicts different geometries for the electrodes. FIG. 2 a depictsa segmented design 30 where each electrode is patterned to includesubstantially straight portions 32, and complementary opposing concavecurvatures 34 a,b that are curved to form an electrode separationgreater than that provided by the substantially straight portions 32.The pattern is repeated through the length of the electrodes. Thedistance between the curved portions affects the signal transmissionsuch that sensor electronics can ascertain the location on the electrodewhere a measurement is being made. In this manner, the signal on averagewould be less affected by those curved portions of the electrode thatwere further apart, so as to serve a similar desired result as theinsulated sections of the electrodes 16 of FIG. 1 .

FIG. 2 b depicts an electrode geometry where the electrodes 36 a,bdiverge from one another over the course of the length of theelectrodes, as they traverse the length of the vessel. In this manner,the signal transmission is affected as a function of length, thusallowing applicable signal electronics to locate the point ofmeasurement, and therefore the point of the regeneration gradient. Itmay be beneficial to have the electrodes in closer proximity at thebottom of the vessel so as to have a more sensitive measurement when theexhaustion wave front eventually reaches this lower portion of the bed.

FIG. 2 c depicts an electrode geometry where a plurality of electrodes38 are presented having different lengths traversing the length of thevessel as another way to ascertain the location of the regenerationgradient.

FIG. 3 depicts a printed electrode geometry 30 produced by silkscreening or printing a silver containing ink 32 directly onto a mylarsheet 34, or printed directly onto a riser tube. The silkscreen printcould be gold or other more noble conductor with a carbon overcoat forabrasion resistance. The silkscreen may then be overprinted with carbon.A noble conductor with a carbon overcoat contributes to the eliminationof oxidation of the conducted metal. The electrode is then attached to ariser tube of a softener, or printed onto the surface of the riser tube.Although less conductive, the carbon provides for more corrosion andabrasion resistance in water applications. Furthermore, the carbon isapplied as a thin coating, and as such will not adversely affect theelectrical integrity of the signal.

FIG. 4 depicts an example of an insulated parallel electrodeconfiguration 40 used to estimate the breakthrough volume. Breakthroughis a measure of the maximum permissible ion leakage requiring theproduction cycle to be shut down. Exemplary dimensions of electrode 40are shown as being 8.6 cm in total length, spaced 0.8 cm apart, andhaving a pair of opposing insulation sheaths about each electrode andbeing 3 cm in length, approximately centered about the top and bottom ofthe electrode. Other dimensions are feasible, and FIG. 4 represents onlyan exemplary embodiment. Utilizing the parallel electrode configuration40 of FIG. 4 , in a test configuration, the system resistance was heldat 50 ohm, frequency at 2 Khz, and input voltage at 500 mV.

FIG. 5 is a graph of the predicted breakthrough of a water softenerusing the longitudinal electrode configuration of the present invention,comparing impedance and the output flow of Ca²⁺ in units of ppm, bothmeasured as a function of time. This graph represents the output of a“digitized” system, where the measuredconductivity/resistivity/impedance between parallel longitudinalconductors is altered by either introducing more space betweenconductors or insulating material at predetermined, discrete intervals.FIG. 5 is a graphical representation of such a digitized system. Theflat portion of the curve, line 50, identifies where the wave front isencompassed by an insulator or at a point of further conductor spacing,and the increasing slope depicts there the wave front has moved past thediscrete insulator or conductor spacing. In this example, the ratio ofthe length of the electrode (until the end of the insulation) divided bythe total length of the electrode is equated to the ratio of the volumeof water passed until the end of insulation divided by the breakthroughvolume.

In prior art applications, the usual procedure during installation is tofeed a total hardness value once into the system, and consider the valueconstant throughout the operational life of the softener. However, asdiscussed previously, the quality of water changes from season toseason, and even within a day, as the supply may comprise differentwater sources. This inaccuracy ultimately results in either hard wateror excess use of salt at the consumer level.

The longitudinal electrode system of the present invention is introducedas a set of two longitudinally placed electrodes attached to a risertube and implanted within a resin bed, wherein the electrodes respond toa change in resin form from Na⁺ to Ca²⁺ and/or Mg²⁺.

FIG. 6 depicts a simplified circuit used to stimulate an electroderesponse (V_(o)) at approximately 100 mV between electrode conductorswithin exhausted resin. The input voltage signal (V_(in)) of thisexemplary embodiment was set at 900 mV at a frequency of 2 Khz. Apreferred 50 ohm system is used for standardized transmission.

The service cycle was carried out with a flow rate of 15 lpm at apressure of 42±3 psi in the upstream of the softener. The outputresponse of the electrode (V_(o)) (output potential in mV) was measuredwith a digital multimeter, and digitally recorded (time (sec) vs. V_(o)(mV)). Plot time vs. V_(o) was converted to volume (L) vs. V_(o) (mV)using an average flow rate calculated during the service cycle. Volumeand TDS of water flowing through softener was recorded at regularintervals. Water temperature of softener downstream was recorded.Upstream and downstream of the softener, water samples were collected atregular intervals for measuring TDS and Ca²⁺, Mg²⁺, and Na⁺ ionanalysis.

Softener testing with the electrodes was carried by using water havingvarious total hardness (25, 15, 10 g) and TDS (˜1000, 1500, and 2000ppm) at various temperatures (10° C., 25° C. and 40° C.).

Testing at Room Temperature and Temperature Compensation

FIG. 7 depicts the response of the electrodes (V_(o)) plotted againstwater volume (L) passing through the resin bed with water quality ofabout 25 g at room temperature (25° C.) and with a TDS of about 1000ppm. Initially it was observed that flow rate (15 lpm vs. 8 lpm) had noeffect on slope of the plot.

Runs 27 and 28 are depicted. The estimated total hardness for each runwas 28.1 g and 27.5 g, respectively at 25° C. The respective actualhardness measured was 25.2 g and 25.6 g for each run, yielding acorrected hardness of 26.0 g and 25.5 g. The range of deviation ofexpected to actual values over eleven different runs was −5.4% to 7.4%.Additional tests were made at 10° C. and 40° C. FIG. 8 depicts a chartidentifying the estimated total hardness, actual total hardness,corrected total hardness, and percent deviation for each run performedat different temperatures.

FIG. 9 depicts the response of the electrode V_(o) (mV) versus the resincapacity (unused) R_(c) (g) for Runs 27 and 28 until breakthrough, bytrimming the initial volume of water. From volume of water (gal) passedthrough the softener and measured total hardness TH (g) of water, resincapacity R_(c) (g) consumed and resin capacity unused or remaining wascalculated. In this manner, the following calculations were made:R _(c)(consumed)(g)=Volume (gal)×TH(g)R _(c)(remaining)(g) at given time=R _(c)(breakthrough)−R _(c)(consumed)at given time

The trend line for the plot of FIG. 9 found a best fit with a polynomial2^(nd) order equation. Similarly, testing with various total hardnessvalues at room temperature (25° C.) were plotted and curve fitting wasdone with polynomial equations. A final Remaining Resin CapacityEquation was derived by averaging all constants.Y=(2.7404x ²)−(692.18x)+41986.2  (1)

-   -   where Y is Resin capacity (R_(c)) remaining in grains; and    -   x is electrode response V_(o) (mV).

The coefficients will vary in measurement for each resin filled vessel.Once the curve fit is established (which is anticipated to be a factorygenerated curve, dependent upon the variations in individual softenervessels), it may be used to predict the resin remaining.

The empirically derived curve provides a predictive way to estimateresin capacity. One such method is to consider the resin capacity atpoints in time t_(o) and t₁. Utilizing a curve fit, such as theexemplary curve of equation (1), the data at the given points in timecan be used to estimate feed water hardness. The capacity measured att_(o) is compared to the capacity at t₁, where a given measured amountof softened water has flowed through the system. The capacity consumedbetween t₀ and t₁ divided by the volume of flow will yield the hardnessconcentration of the feed water.

Equation (1) estimates the resin capacity (R_(c)) remaining at any giventime. The total hardness (TH) of water flowing through resin bed can beestimated as follows:TH(g)=R _(c)(g) used/[volume (gal) pass through resin bed]=ΔR _(c)/ΔV  (2)

As noted, the electrodes were tested at various temperatures (10° C. and40° C.) other than room temperature, and at different total hardnesslevels (10 g, 15 g, and 25 g). A general linear equation was establishedfor temperature compensation of the electrode response (V_(o)):V _(o(25)) =V _(ot)[1+0.02(t−25)]  (3)

where V_(ot) is the electrode response at a given temperature; and

-   -   V_(o(25)) is electrode response at 25° C.

Equation (3), referred to as the temperature compensation equation,normalizes V_(o) of any temperature to V_(o) at 25° C. Afteraccommodating for temperature compensation, resin capacity remaining andthe total hardness of water can be estimated by using equations (1) and(2).

As an illustrious example, run 27 identified in FIG. 4 along with anadditional run 64 are compared by recording two to three V_(o) values toestimate resin capacity (R_(c)) and total hardness (TH) as shown in FIG.10 (Table 1). A clear competence in using equations (1) and (3) wasobserved from FIG. 11 . Plots in FIG. 11 depict temperature compensatedcalculations for runs 27 and 64 from 40.8° C. to 25° C. utilizingequations (1) and (3).

In order to improve the method of estimation, a correction factor wasderived from experimental data at various temperatures by regressionanalysis.TH_(corrected)(g)=4.7003+0.7944*estimated hardness(g)−0.04097T(°C.)  (4)

The correction factor improves the accuracy of the proposed method asshown by limiting deviations to less than or equal to 10%, as depictedin Table 2 of FIG. 12 .

FIG. 13 presents a comparison of TH deviation % with and without thecorrection factor over several tests conducted at various temperatures(approximately 10° C., 25° C. and 40° C.) with different TH (about 10 g,15 g, and 25 g) but limited to TDS of approximately 1000 ppm.

Effects of TDS on Electrode Response

TDS is a common variable of water quality and its effect must beconsidered with respect to the electrode response. As given earlier,water with three different TDS values of about 1000, 1500, and 2000 ppmwas considered by fixing total hardness (TH) as 25 g and temperature (T)at about 25° C.

Initial water values for total hardness (TH) was about 25 g and 1000 ppmof TDS. Any changes from this water quality required an addition ofdeionized water (with 1 or 2 μS/cm) and NaCl (grade purity >99.5%). Tobring TDS to 1500 and 2000 ppm extra NaCl was added to water and mixedwith a recirculation pump for about three hours by checking TDS atregular intervals.

Results of these tests are depicted in FIGS. 14 & 15 . FIG. 14 depictsthe results of output potential V_(o) (mV) as a function of volume (L),and indicating breakthrough for three different runs. FIG. 15 depictsthe results of resin capacity R_(c) as a function of V_(o) (mV). Thisdemonstrates that TDS is observable as offset change with a more limitedslope change, in contrast with effect of temperature, which contributesmore to slope change. The effect of TDS on slope was considered minimal.

Similar results are depicted in FIG. 16 , which was derived usingtemperature compensation equation (3). FIG. 16 depicts the effects ofTDS on R_(c) versus V_(o), after temperature compensation.

From the tests conducted with 1500 ppm and 2000 ppm of TDS, the THdeviation (%) results with and without a correction factor (using eq. 4)are shown in FIG. 17 . A clear improvement of estimated TH with theexemplary sensor was observed, confirming that the method developed hasminimal TDS effect.

Finding Early Breakthrough for the Softener

Typical softener flow meters are unable to measure flow below 0.3gal/min. This means a considerable volume of water below this flow ratemay flow through the softener and consume resin capacity. Over a periodof several regenerations, the softener may provide untreated water.

One solution presented by an embodiment of the present invention is todecrease the electrode length or limit the electrode length above thelower diffuser, making it possible to observe a stable V_(o) beforebreakthrough.

FIG. 18 presents an electrode configuration for establishing an earlybreakthrough point. Electrode 70 is terminated a 10 cm distance from thelower end of the electrodes to the lower diffuser.

As depicted in FIG. 19 , fixing electrodes 10 cm above the lowerdiffuser stabilizes the V_(o) reading by approximately 8% by volumebefore breakthrough (soft water with threshold hardness of ˜1 g).

Once the hardness front crosses the lower tip of electrode, a change inresponse with change in resin bed resistance will ultimately stabilizeand reach the flat region of plot as shown in FIG. 19 . At this point oftime, regeneration can trigger with extra fill time and fill volume toshift the operating region of resin bed back to normal. This will ensurealways to provide a user with soft water while shifting the operatingregion of resin bed, and further to correct for the volume of waterpassing through resin bed.

Effect of Flow Rate and Flow Conditions

To better understand the effects of flow rate on an electrode embodimentof the present invention, a service cycle was carried at different flowrates of 15 lpm and 8 lpm with continuous flow. From these tests, it wasdemonstrated that flow rate has no effect on slope of plot with respectto volume of water passed and R_(c) remaining. FIG. 20 depicts theeffect of flow rate on V_(o) v. V_(L), and FIG. 21 depicts the effect offlow rate on R_(c) v. V_(o). This is no appreciable difference betweenthe respective curves.

The longitudinal impedance sensor was tested under various flowconditions/patterns, e.g., continuous flow (CF), and intermittent flow(IF), representing an interval of flow for 10 minutes and no flow for 10minutes. No change in slope as a function of flow condition was observed(FIGS. 22 and 23 ), which included the changes with flow rates. FIG. 22depicts the effect of flow conditions on V_(o) v. V_(L), and FIG. 23depicts the effect of flow conditions on R_(c) v. V_(o).

Time and Volume Required to Reach Uniform Temperature of Resin Bed

Usually softener and resin bed are at ambient temperature or roomtemperature whereas, water might be at a different temperature. V_(o) ofelectrode is predicated upon an average resistance of resin bed anddependent on resin bed temperature. Hence, it is necessary to considerthe uniform temperature of the resin bed required to record the properresponse of electrode.

As an illustrative example, three temperature sensors (Pt100) wereinstalled in the resin bed at various depths (top, middle, and bottom ofthe electrode depicted in FIG. 18 ) to investigate the temperatureuniformity of resin bed. Various volumes of water at different flowrates were passed through the resin bed while recording the temperature.The temperature of the water used for testing was varied, with lowtemperature at approximately 11° C., room temperature at approximately26° C., and high temperature at approximately 39° C.

It was found that an optimal time of 30 minutes at a volume of 20 L(four times the softener net volume) was sufficient to obtain uniformtemperature, irrespective of water temperature. FIG. 24 depicts a plotto find early breakthrough measuring cold water temperature versus time.FIG. 25 depicts a plot to show the operational window for the electrodeof the present invention, plotting optimal time for uniform temperatureas a function of volume of water passed through the resin bed.

In the aforementioned plots, uniform bed temperature was determined whenthe temperature difference between the sensors was ≤0.5 (i.e., thelimitation of Pt100 temperature sensor).

Referring to FIG. 25 : a) if 40 L or greater volume of water passedthrough the resin bed (8 times of net softener volume) the outputresponse of the electrodes could be recorded immediately irrespective ofwater temperature; and b) if the water temperature is at 40° C. or atroom temperature, the resin bed reaches a uniform temperature in 20minutes with 15 L (three times the net softener volume).

Blending

Certain markets, such as European markets, remain interested in blendingsoft water with hard water (upstream) to get small quantities ofhardness ions while avoiding some effects of the silky nature of treatedwater. Thus, the valve of the current invention is adjusted to set arequired blending percentage or desired hardness downstream of thesoftener. In testing the sensor and method for blending, the totalhardness, TH, was limited to 2 g and 5 g of downstream water.

The blending ratio was calculated from the estimated TH and required THof blended water. The ratio of actual TH measured to blending ratiogives a TH of blended water. Total hardness of blended water fromestimated total hardness values with correction factor (equation (4))was plotted as shown in FIGS. 26 and 27 .

FIG. 26 depicts a number of runs for the total hardness of blended waterfor 2 g and 5 g respectively at 10° C., 25° C., and 40° C.

FIG. 27 depicts a number of runs for the total hardness of blended waterwith high TDS for 2 g and 5 g respectively at 10° C. and 40° C.

The calculated total hardness of the blended water was limited to belowone half a grain in most instances.

Flow Procedure for Estimating Total Hardness of a Softener Upstream

FIG. 28 is a flow chart depicting the flow procedure for estimating thetotal hardness upstream of the softener using a longitudinal impedancesensor.

Referring to FIG. 28 , in a first step 100, the electrode height in theresin bed is set above the lower diffuser to identify the breakthroughearly, generally by about 8%. Next, in step 110, the service cycle isrun at 25° C. with a total hardness of 25 g and 1000 ppm TDS water. Theelectrode response is plotted (V_(o) in mV) versus volume of water flowthrough the softener (V_(L)).

In step 120, the resin capacity R_(c) remaining is plotted versus V_(o).The resin capacity remaining is equated to the resin capacitycorresponding to breakthrough minus the resin capacity consumed, wherethe resin capacity consumed is the product of the volume (gallons) andtotal hardness (grams), i.e., R_(c-consumed)=Volume (gal)×TH (g).

Next, step 130, the resin capacity, R_(c), is derived from equation (1).A trend line is calculated for best fit. An empirical derivation of bestfit plots is utilized. In the instant case, this fit has been shown tofollow the equation:Y=2.7404x ²−692.18x+41986.2  (5)

The coefficients will alter and depend upon the vessel being measured,which is anticipated to be performed in a factory setting. In step 140,the V_(o) versus V_(L) plots are obtained for 10° C. and 40° C.

Next, step 150, the V_(o) v. V_(L) plot is compensated by using equation(3) to obtain V_(o25).

The method steps above are repeated with total hardness values of 10 gand 15 g (step 160). In step 170, the total hardness TH(g) is estimatedfrom the ratio of the change in resin capacity (ΔR_(c)) and change involume (ΔV (gal)).

A regression analysis is performed (step 180) where: Y_(range)−ActualTH; and X_(range)−temperature and estimated TH are considered.

Last, in step 190, the correction factor was derived from the regressionanalysis (equation (4)):Corrected TH(g)=4.7003+estimated hardness(g)−0.04097*temp(° C.)  (6)

The service cycle was continued slightly after breakthrough until 40 ppmof Ca²⁺ concentration in output flow was observed (downstream of thesoftener) with V_(o) being stable.

It is noted that the aforementioned polynomial is a model of a specificsensor in a specific unit that relates the capacity remaining in the bedto the measured V_(o). The remaining capacity can be determined by usingthe model at any point in the exhaustion process. The polynomial ispredetermined, i.e., factory set, predicated upon the different watersoftener vessel variables.

Using this control algorithm, it is possible to keep track of the flowthrough the softener in gallons of water/unit time, and having a presethardness value, the capacity exhausted from this water flow can becalculated. With knowledge of prior softener regeneration and how muchcapacity is present in the regeneration, it is possible to estimate howmany gallons of water remain, when the next regeneration sample will beneeded, and how much salt will be required to generate enough capacityto keep the softener running for some expected period of time.

Using the V_(o) value from the sensor, it is possible to determine howmuch capacity is remaining in the softener bed. The response is somewhatunpredictable (noisy) for the first few gallons, insomuch as rinsing ofthe last of the regenerating salt from the unit affects the resistancevalue from that rinse more than from bed exhaustion, but once theinitial flow is complete, V_(o) may be accurately measured, and theremaining capacity in the bed may be determined. Subsequently, thesoftener is allowed to operate producing some measured amount ofsoftened water. V_(o) is measured and the remaining capacity isdetermined.

The difference in the starting capacity and the remainingcapacity/volume of flow provides for the inlet hardness. The remainingcapacity/inlet hardness provides the remaining volume capacity of thesoftener operating with water at a current hardness level. In thismanner, the instant invention yields a real time measurement ofremaining capacity that can be coupled with a time/flow rate measurementto establish total flow between capacity measurements, which determinesthe residual capacity in the bed and the rate of capacity consumption.This allows for predicting when to initiate regeneration.

Complete Cycle of Operation

A complete cycle of operation is described, referring to the numberedparts in the attached drawings.

First, a new softener with fresh resin 12 is installed. After plumbingfor the brine or regeneration solution 5, the regeneration waste stream6, the hard water inlet 7, the soft water outlet 9, and blending valve8, water containing hardness (calcium, magnesium) and potentially ironis allowed to enter through the inlet 7. This water may be channeledfrom either bottom up 26 or from top down depending on the softenerdesign.

The “hard” water comes in contact with the resin 12 and hardness andiron ions are exchanged for sodium ions on the surface of the resin.

Impedance sensor 14 monitoring impedance (resistivity, conductance,capacitance) measures the change in the resin charge as sodium ions areexchanged.

As the resin is exchanged at the top (or bottom depending on softenerdesign), hard water passes through the exchanged resin and a “hardnessfront” 12 c forms at the boundary of depleted resin 12 b that has beenexchanged and the resin that has not been exchanged 12 a.

The sensor 14 monitors this hardness front through the systemselectronics, processor, and associated algorithm(s), which also monitorthe flow through the system.

This information, along with historical data on water usage by time ofday is used to trigger regeneration at a convenient time of the day whenwater consumption is low since the system must be placed in bypass bythe softener valve 4. Once a regeneration is triggered, the inflow intothe softener is stopped in the valve 4 and regenerant (typically asaturated sodium solution) is pumped into the resin bed 12 from theopposite direction used during normal operation. This regenerant exitsthe resin bed and is typically sent to the regeneration waste stream 6(i.e., the drain).

The sensor 14, electronics, and processor will monitor this process todetermine when the regenerant trailing edge leaves the stack.

The next step is a slow rinse followed by a fast rinse, both of whichare monitored by sensor 14 to determine when those processes arecompleted based on conductivity changes in order to minimize waterusage.

Following the rinse cycles, valve 4 is set to operating mode. Hard waterenters the softener and depending on how much water enters, which ispreferably monitored by a flow sensor, and the identification of a newhardness front, the system can calculate the next regeneration event.

It is noted that during operation, the amount of hardness could changeand the hardness front would slow down. However, based on the foregoingmeasurements, it is possible for the electronics and on-board processorto determine the hardness (hardness number) of the water.

This hardness number could also be used by the softener's processor andalgorithm to adjust (automated) blending valve 8 if 100% softened wateris not desirable. Being able to calculate the hardness of the incomingwater is critical to the bypass valve's proper metering of untreatedwater to achieve the desired output hardness.

This process would also allow the automatic startup of a softenerwithout having to input the hardness of the incoming water at the timeof installation since the system can calculate the hardness based on thesensor's monitoring of the resin bed's depletion as a function rate offlow.

While the present invention has been particularly described, inconjunction with a specific preferred embodiment, it is evident thatmany alternatives, modifications and variations will be apparent tothose skilled in the art in light of the foregoing description. It istherefore contemplated that the appended claims will embrace any suchalternatives, modifications and variations as falling within the truescope and spirit of the present invention.

Thus, having described the invention, what is claimed is:
 1. Anapparatus for producing a signal indicative of a state of the exhaustionor depletion of an ion exchange material in a vessel, comprising: saidvessel having an axial length traversing in a longitudinal directionfrom approximately vessel top to approximately vessel bottom; said ionexchange material within said vessel; a conductivity, resistivity,and/or impedance sensor including at least two electrodes in electricalcommunication with one another, wherein said electrodes extendcontinuously approximately throughout said axial length of said vesselin said longitudinal direction; and a controller for producing a signalto said electrodes and/or receiving a signal from said electrodesrepresenting a conductivity, resistivity, or impedance measurementbetween said electrodes, and determining said exhaustion or depletion ofsaid ion exchange material from said electrodes representing saidconductivity, resistivity, or impedance measurement.
 2. The apparatus ofclaim 1 including: a hard water input; a soft water output; aregeneration supply solution for regenerating the ion exchange material;a drain or regenerating waste stream; a water softener or regenerationvalve; and an admixing or blending device for mixing output fluid. 3.The apparatus of claim 1 wherein each of said electrodes comprise a wireconductor formed of conductive material which are situated to rungenerally parallel to one another.
 4. The apparatus of claim 1 whereinsaid electrodes traverse along or inside a tube internal to said vesselwhile in contact with said ion exchange material, and are set apart assaid electrodes progress approximately throughout said axial length ofsaid vessel in said longitudinal direction.
 5. The apparatus of claim 1wherein said electrodes progress approximately throughout said axiallength of said vessel in said longitudinal direction approximatelyparallel to one another.
 6. The apparatus of claim 1 wherein saidelectrodes progress approximately throughout said axial length of saidvessel in said longitudinal direction, wherein each electrode is formedof sequential curved and straight segments such that said curvedsegments of each electrode are parallel to one another and said straightsegments of each electrode are parallel to one another.
 7. The apparatusof claim 1 wherein said electrodes progress approximately throughoutsaid axial length of said vessel in said longitudinal direction, whereinthe electrodes are separated a predetermined distance that variesthroughout said axial length of said vessel in said longitudinaldirection.
 8. The apparatus of claim 1 including a plurality ofelectrode pairs having different lengths extending in the longitudinaldirection such that at least one electrode pair progresses approximatelythroughout said axial length of said vessel in said longitudinaldirection, and other electrode pairs have varying lengths shorter than alongest length electrode pair.
 9. The apparatus of claim 1 wherein saidcontroller includes operational software to calculate the averageimpedance, conductivity, or resistivity of said ion exchange materialwithin said vessel from detected measurements of impedance,conductivity, or resistivity, respectfully, wherein said averageimpedance, conductivity, or resistivity is proportional an amount ofregeneration of said ion exchange material within said vessel.
 10. Theapparatus of claim 1 wherein said controller includes operationalsoftware to track resistivity of the ion exchange material as a functionof water volume through said apparatus.
 11. The apparatus of claim 1wherein said controller includes operational software to calculate andmonitor the relationship between resistivity of said ion exchangematerial as a measured response from said at least two electrodes andcapacity of said ion exchange material being depleted, based on apredetermined formula as a function of said measured response.
 12. Theapparatus of claim 1 wherein said controller includes operationalsoftware to compare input volume of water flowing into said vessel tocapacity of ion exchange material being used or depleted, and from thiscomparison, compare said capacity to resistivity measured by saidconductivity, resistivity, and or impedance sensor, such that capacityof said ion exchange material can be ascertained in-situ.
 13. Anapparatus for producing a signal indicative of the state of theexhaustion or depletion of an ion exchange material in a vessel,comprising: said vessel having an axial length traversing in alongitudinal direction from approximately vessel top to approximatelyvessel bottom; said ion exchange material within said vessel; aconductivity, resistivity, or impedance sensor for determining saidexhaustion or depletion of said ion exchange material, saidconductivity, resistivity, or impedance sensor including at least twoelectrodes in electrical communication with one another, wherein saidelectrical communication between said electrodes is interrupted by aplurality of insulators spaced apart axially to form non-conductive gapsbetween said electrodes that extinguish conduction between adjacentinsulation portions on each electrode to enable segment-wise continuouselectrical communication between electrode portions not interrupted byinsulators throughout said axial length of said vessel in saidlongitudinal direction; and a controller for producing a signal to saidelectrodes and/or receiving a signal from said electrodes representing aconductivity, resistivity, or impedance measurement between saidelectrodes, said controller determining said exhaustion or depletion ofsaid ion exchange material from said conductivity, resistivity, orimpedance sensor signal from said at least two electrodes.
 14. Theapparatus of claim 13 including: a hard water input; a soft wateroutput; a regeneration supply solution for regenerating the ion exchangematerial; a drain or regenerating waste stream; a water softener orregeneration valve; an admixing or blending device for mixing outputfluid; and a lower diffuser plate.
 15. A water treatment system having atank containing a particle bed for removing minerals from water flowingthrough the tank, and a measuring apparatus for measuring conductivity,resistivity, and/or impedance within the tank, comprising: a hard waterinput; a soft water output; said particle bed including ion exchangematerial within said tank; a regeneration supply solution forregenerating said ion exchange material; a drain or regenerating wastestream; a water softener or regeneration valve; an admixing or blendingdevice for mixing output fluid; said tank having an axial lengthtraversing in a longitudinal direction from approximately tank top toapproximately tank bottom; a conductivity, resistivity, or impedancesensor for determining exhaustion or depletion of said ion exchangematerial, said conductivity, resistivity, or impedance sensor includingat least two electrodes in electrical communication with one another,wherein said electrodes extend continuously approximately throughoutsaid axial length of said vessel in said longitudinal direction, saidelectrodes in contact directly with said ion exchange material forimpedance measurements or indirectly with said ion exchange material forconductivity measurements; and a controller for producing a signal tosaid electrodes and/or receiving a signal from said electrodesrepresenting a conductivity or impedance measurement between saidelectrodes, said controller determining said exhaustion or depletion ofsaid ion exchange material from said conductivity, resistivity, orimpedance measurements from said at least two electrodes.
 16. The watertreatment system of claim 15 including a tube traversing in saidlongitudinal direction from approximately said tank top to approximatelysaid tank bottom, said tube directing fluid flow either upwards towardssaid tank top, or downwards toward said tank bottom.
 17. The watertreatment system of claim 16 wherein said electrodes are supported bysaid tube.
 18. The water treatment system of claim 15 whereinconductivity measured by said electrodes corresponds to a change in ionexchange material from Na⁺ to Ca²⁺ and/or Mg²⁺.
 19. The water treatmentsystem of claim 15 wherein said electrodes extend approximately twocentimeters from a topmost portion of said particle bed to twocentimeters from a bottommost portion of said particle bed in saidlongitudinal direction.